Cocoa, chimpanzees, and the restorative value of gorilla dung…

Having reached mammals in our meanderings, and the human involvement in global plant dispersal (admirably explored in Michael Pollan’s book The Botany of Desire) notwithstanding, we couldn’t ignore our nearest and dearest living relative, the critically-endangeredchimpanzee (Pan troglodytes verus), in this curious catalogue of –chory. Kimberley Hockings et al. report on the dispersal of human-cultivated cocoa (Theobroma cacao) by wild chimpanzees in a forest-farm matrix habitat in the village of Bossou (southeastern Republic of Guinea, West Africa) (International Journal of Primatology38: 172–193, 2017; doi: 10.1007/s10764-016-9924-y).

Although humans are quite adept at tending and dispersing this plant, the chimpanzee contribution – averaging 407 m (range: 4–1130 m) from the cocoa plantation – is arguably a bonus from the plant’s perspective. However, unless the seedlings that developed from translocated seeds were in an established cocoa plantation – where human farmers would tend to them – they did not set fruit. So, a human association is still needed. But, and almost straying into territory that considers the rights of non-human animals, Hockings et al. conclude that their “local-scale findings emphasize the complex behavioral and ecological interconnections between coexisting humans and primates in agricultural landscapes and generate interesting questions regarding primate niche construction and crop “ownership” related to who “plants” the crop.”

Emphasising the important role of primates in plant dispersal more generally, Barbara Haurez has examined the part played by western lowland gorillas (Gorilla gorilla gorilla) in Gabon (Africa). Her conclusion is that these primates are important to the regeneration and dynamics of Congo Basin forests. Unfortunately, in the wild, the western lowland gorilla is critically endangered, due to such threats as their capture, killing, and cooking by humans who consider eating such ‘bushmeat’, a highly-prized ‘delicacy’. But not only is such thoughtless slaughter bad for the gorillas, it is not good for the ecology of the areas where these magnificent mammals live and where they help to maintain plant numbers and diversity. One would like to think that work of scientists such as Huarez will encourage “the implementation of gorilla conservation strategies as critical to ensuring the preservation of tropical forest ecosystems”.

And it’s not just the mobile, living gorillas that have value for plant dispersal and forest regeneration. Augustin Basabose considers the value of seed-loaded dung of apes. To date, planting native tree seedlings is the most common strategy for restoring tropical forests. An additional strategy, proposed by Basabose, is to use intact seeds found in gorilla and chimpanzee faeces as a cost effective and non-invasive way to restore native forested habitats in the Kahuzi-Biega National Park, a UNESCO World Heritage Site. Preliminary results are encouraging with very high % germination of such dung-extracted plant species as Allophyllus kivuensis and Syzygium parvifolium.

However, rather than the time-consuming, labour-intensive practice of searching for seeds within, and extracting them from, the ape faeces, mightn’t a better way be to spread the balls of dung over the area to be replanted letting nature take its course and allowing the seeds to germinate naturally amongst the nutrient-rich faecal material? In that way, a more natural planting could be achieved with the seedlings emerging from the dung competing with each other so that only the fittest individuals survived. Plus, by leaving the seeds within the excrement they will have the added boost of extra – and free – nutrients to get them started on their journey of growth and establishment. One can even imagine balls of dung being liberally strewn over the area to be revegetated in a quite literal scat–tergun way…

[This is part 3 of a multi-part series of short items celebrating the creatively imaginative and enterprising ways in which plants dupe poor unsuspecting animals into doing their sexual bidding…]

Nigel is a botanist and full-time academic at Bath Spa University (Bath, near Bristol, UK). As News Editor for the Annals of Botany he contributes the monthly Plant Cuttings column to that august international botanical organ. His main goal is to inform (hopefully, in an educational, and entertaining way...) about plants and plant-people interactions.

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